The goal for the proposed research is to better understand the descending motor systems that participate in the control of hand and arm movements. The proposed experiments will test the general hypothesis that pontomedullary reticular formation (PMRF) neurons participate in the control of hand movements. These experiments will examine 1) whether PMRF neurons discharge during hand movements, and 2) whether PMRF neurons have functional connections with hand and forearm motoneurons. These two specific aims will be addressed by recording neural activity simultaneously with electromyographic activity from upper limb muscles bilaterally as subjects perform a reach to grasp task. In the reach to grasp task, subjects will reach to different spatial locations where they will perform two different hand movements. Neural activity recorded in the reach to grasp task will be analyzed with the double dissociation method to determine whether a neuron's discharge is related to posture and reaching or hand-grasping movements. Functional connections between PMRF neurons and spinal motoneurons will be examined by compiling spike and stimulus triggered averages of rectified electromyographic activity recorded from arm, forearm, and hand muscles. Task related neurons will be further examined for functional connectivity by performing cross-correlations with simultaneously recorded upper limb electromyographic activity to determine whether PMRF neuron discharge relates to electromyographic activity in the muscles that control hand movements. The resulting cross-correlation values will be used to calculate functional linkage vectors in order to quantify and compare each neurons relationship among all simultaneously recorded muscles. PUBLIC HEALTH RELEVANCE: Every year, thousands of people living in the United States suffer a nervous system injury that causes paralysis or weakness in the upper extremity. Consequently, these individuals must relearn movements necessary to their daily routines, such as washing, eating, or dressing. Findings from these studies should improve rehabilitation strategies for individuals that have suffered stroke and central nervous system injury.